[HLP]Object animate when object falls.

I need it so when an object falls (with alot of particles) that it hits an object and animates it. But it only animates when it's < a number of objects. If that makes sense.
In other words I want something to animate with a certain amount of particles hit it.
Thank You,
Zack
In other words I want something to animate with a certain amount of particles hit it.
Thank You,
Zack